(a) Field of the Invention
The present invention relates to a protocol executing system for processing protocol PDUs (Protocol Data Units). More specifically, the present invention relates to a method for executing protocols more flexibly and transparently according to the protocol PDU encoding/decoding method.
(b) Description of the Related Art
The encoding/decoding methods for generating protocol PDUs are classified into a binary-based method and a text-based method. The binary-based method, which method is encoding/decoding PDUs using binary values, reduces the size of the PDUs to allow a high performance with the use of small-sized memories but it is difficult to debug. The binary-based method is generally used as an encoding/decoding method for protocols that have complicated and long protocol grammar of the PDUs. On the other hand, the text-based method allows the users to immediately understand PDUs and has no debugging difficulty, making it possible to develop protocols in a short time. The text-based method, which disadvantageously takes a long decoding time for texts relative to the binary-based method, is used as an encoding/decoding method for protocols that have simple and short protocol grammar for PDUs.
The protocols currently in use have such a high adaptability that either the binary-based method or the text-based method can be selected according to the environment of the protocol-executing system. A specific example of the binary-based method includes Abstract Syntax Notation One (hereinafter referred to as “ASN.1”). The ASN.1, which describes an abstract syntax so as to implement an encoding/decoding method regardless of programming language, is disclosed in the standard by ITU-T. A specific example of the text-based method includes ABNF (Augmented Backus-Naur Form) suggested in the RFC2234 standard by IETF.
When a PDU data structure processed by a protocol executing block is subordinated between the ASN.1 encoding/decoding block and the protocol executing block, the subordinate addition of the ABNF-based encoding/decoding method may cause the following problems.
When the PDU data structure of the ABNF encoding/decoding block is set to the ASN.1 data structure, the PDU data structure is subordinate to the ASN.1 type. So, the ABNF protocol PDU encoding/decoding block has to be modified for processing the data structure whenever the ASN.1 protocol PDUs are changed.
Moreover, the load of the protocol executing block increases with different PDU data structures.